Comment by Xylakant
16 hours ago
it also reduces peak load - you can heat water up slower with a lower powered heater. I have a 35 liter warm water tank in my garden shed that pulls about 3.5kw - an equivalent on demand heater would need 14kw or more.
I don't see why that matters. You use the same amount of energy and the demand is smoothed out at grid scale (yes I know about tea in ad breaks).
You can get things like cheaper overnight tariffs when the demand is lower - if you have some sort of storage system - like a hot water tank - in effect the electricity company is distributing some of that smoothing function to things like hot water tanks, storage heaters or batteries.
If you have your own solar ( either direct solar water heating, or solar electricity generation ), the hot water tank is a simple, cheap, reliable energy store.
Sure capacity isn't that great - but pretty much every house in the UK used to have one, so it adds up.
Houses in the UK typically have 100A supply and the whole local grid is sized assuming people use relatively small amounts of electricity. If everyone gets an electric car and a massive heat pump, lots of local transmission will need upgrading
Right but unless everyone is drawing large amounts of power at the same time it doesn't matter if you use 1kW for 10 hours or 10kW for 1 hour. To the grid they look the same.
One interesting case where "at the same time" actually does happen is overnight car charging. Some chargers are configured to start charging exactly when a cheaper tariff kicks in, which causes big transient issues for the grid. I think modern chargers have a random delay to help with that.